Travel in Space: To the Moon and Beyond

The rocket engine, with its steady roar like that of a waterfall or a thunderstorm, is an impressive symbol of the new space age. Rocket engines have proved powerful enough to shoot astronauts beyond the earth's gravitational pull and land them on the moon. We have now become travelers in space.

空间旅行：到月球和更远的星球上去

火箭发动机带着瀑布和雷鸣般深沉的轰呜，是航天新时代的象征，给人以深刻的印象。火箭发动机已经证明有足够的动力，能将字航员发射到地球引力作用范围之外，并使之登月。现在人类已经可以在太空中遨游了。

Impressive and complex as it may appear, the rocket is a relatively simple device. Fuel that is burned in the rocket engine changes into gas. The hot and rapidly expanding gas must escape, but it can do so only through an opening that faces backward. As the gas is ejected with great force, it pushes the rocket in the opposite direction.

There are many problems connected with space travel. The first and greatest of them is gravity. If you let your pencil drop to the floor, you can see gravity in action. Everything is held down to the earth by magnetic force. The weight of something is another way of describing the amount of force exerted on it by gravity. A rocket must go at least 2500 miles an hour to take anyone beyond the gravity of the earth into space.

尽管火箭看起来也许会给人深刻的印象，并且似乎很复杂，但它却是一种相当简单的装置。燃料在火箭发动机里燃烧时变成燃气。这种灼熟的迅速膨胀的燃气必须排走，但它只能从向后的出口中排出。当燃气以巨大的力量排出时，便推动火箭朝相反的方向飞行。

空间旅行遇到的问题很多。其中，首要的也是最严重的问题是引力。当铅笔掉到地上时，你就会发现是引力在起作用。世上万物都被磁力吸引在地面上。物体的重量是引力施加在该物体上的力的大小的另一种说法。火箭的速度至少必须达到每小时2500英里，才能把人带出地球引力的作用范围进入太空。

Another problem is the strain that a person is subjected to when a rocket leaves the ground. Anything that is not moving tends to resist movement. As the rocket leaves the ground, it pushes upward violently, and the person in the nose is pushed back against the chair. During this thrust, gravity exerts a force on the body equal to nine times its normal force.

Once out of the earth's gravity, an astronaut is affected by still another problem --- weightlessness. Here,if a pencil drops, it does not fall. If a glass of water is turned upside down, the water will not fall out. All of us who are used to gravity expect things to have weight and to fall when dropped. Our bodies, which are accustomed to gravity, tend to become upset in weightless conditions. Recent long flights have shown that the body needs special exercise in a spaceship.

另一个问题是火箭离开地面时人所经受的过度受力状态。凡是静止的物体都会抵抗运动。当火箭离开地面时，火箭猛烈地向上推，于是便迫使位于火箭头部的宇航员向下紧紧抵着座椅。在这种猛烈推动的过程中，引力在人体上施加的力九倍于正常情况下人体受到的力。一旦脱离了地球的引力作用之后，宇航员又会遇到另一个问题一失重状态的影响。这时，铅笔掉下不会下落，一杯水上下颠倒过来，水不会流出。人们已习惯于重力作用，因此，对物体有重量，扔掉就会坠落这些现象都已习以为常。人体也因为习惯了引力，所以，在失重状态下往往会失常。最近进行的长时间飞行已经证明，人体需要在宇宙飞船上进行专门的训练之后才能适应失重环境。

Cosmic rays and tiny dust particles also raise a problem. Outer space, which has no air, is filled with both of these. The dust particles can damage the front end of the rapidly moving spaceship. The cosmic rays,though they are invisible to the naked eye, can go through the ship and the astronauts themselves. No one is sure what damage the cosmic rays can do to a human being, but scientists feel that brief exposure is probably not very harmful.

宇宙射线和尘埃也是个问题。外层空间虽然没有空气，但却充满了这两种东西。小尘埃可损坏飞速飞行中的宇宙飞船的前端；而宇宙射线尽管肉眼看不见，却能穿过飞船和宇航员本人的身体。宇宙射线会对人类造成什么样的损害，现在无论谁都说不清楚，不过，科学家认为短暂地照射一会儿或许危害不十分大。